1. Field of the Invention
The present invention relates to a novel bacterial strain, a process for degrading at least one of aromatic compounds such as phenol, cresol, etc., and halogenated organic compounds, such as trichloroethylene (TCE), dichloroethylene (DCE), etc. using the microorganism, and process for remedying polluted environment, in particular, soil, sewage, waste water, and gases containing aromatic compounds or halogenated organic compounds.
2. Related Background Art
In recent years, environmental pollution with chloroorganic compounds, which are harmful to living things and difficult to decompose, has become a major problem. In particular, the soil in the manufacturing area of the paper and pulp industry, or the precision machinery and related industries is considered to be polluted with aromatic compounds, such as phenol, cresol etc., and chloroorganic compounds, such as chlorinated aliphatic compounds, for example, trichloroethylene (TCE), dichloroethylene (DCE), etc. In fact, reports on environmental investigation have revealed that such compounds are detected.
It is supposed that the chloroorganic compounds in soil are dissolved in groundwater etc. via rainwater etc. to spread all over the area.
There is a suspicion that these compounds are carcinogenic, and these compounds are quite stable in environment, so that the pollution of groundwater which is used as a source of drinking water has become a social problem.
As described above, removing the chloroorganic compounds and purifying groundwater by decomposition is an important problem in view of the protection of environment, and the various purification technologies have been developed.
For example, absorption treatment using activated carbon and decomposition treatment using radiation or heat have been attempted. The costs and/or the operations of these treatments, however, are not practical.
On the other hand, it has been reported recently that some microorganisms are capable of decomposing volatile chloroorganic compounds which are stable in environment, such as TCE, and the study of utilizing them in practice has already been started. This technique is called bioremediation, and has the following advantages:
(1) By using appropriate microorganisms, chloroorganic compounds can be decomposed into harmless substances.
(2) In principle, no special chemicals are required.
(3) The labor and cost of maintenance can be reduced.
(4) Even the chloroorganic compounds of low concentration can be completely decomposed and removed.
As the study of such bioremediation for practical use progresses, microorganisms powerfully decompose aromatic compounds and volatile chloroorganic compounds in the soil, which are the core of the technique, are strongly required.
Vacuum abstraction, for example, is a conventional method at present for removing volatile chloroorganic compounds in soil. In this method, first an abstraction well is dug, and then such compounds are sucked and removed from the soil using a suction pump. The extracted compounds, however, still exist in the gas phase, being undecomposed. In other words, the pollutant is merely moved from the soil to the gas phase, leaving the serious problem that volatile chloroorganic compounds remains even after the abstraction. This is not only the problem of soil pollution but that of air pollution as well. Polluted air includes, for example, the air polluted with volatile chloroorganic compounds generated in the plants of the high technology industry. Such polluted air must not be released into the atmosphere or environment unless it undergoes some proper treatment to remove the volatile chloroorganic compounds.
At present, the liquefaction treatment and the adsorption treatment with activated carbon are known as the methods for removing volatile chloroorganic compounds in gas phase. Adsorption treatment, however, still has the problem of regeneration of the used activated carbon. Liquefaction treatment also has some problems when it is applied to the treatment of volatile chloroorganic compounds. That is, the treatment is inefficient because of the low concentration of the pollutant in gas phase, in addition, it requires a large-scale equipment resulting in high cost. Furthermore, these treatments are not the true solution to the pollution problem because they merely remove volatile chloroorganic compounds, but do not decompose them. Thus, strongly needed are measures excellent in operation, low in cost, and enabling the complete degradation of volatile chloroorganic compounds into harmless substances.
As such bioremediation technique, for example, the practical use of a bioreactor for gas phase pollution, has been developed, microorganisms having a powerful decomposing activity toward the volatile chloroorganic compounds in soil, the core of the technique, are more and more required.
At present, almost all the microbial strains studied for the bioreactor to decompose the volatile chloroorganic compounds in gas phase, are methane producing bacteria. These bacteria require methane or methanol when decomposing volatile chloroorganic compounds. The presently known strains are not satisfactory in practice from the viewpoint of gas phase treatment or pollutant decomposition, and novel ones are needed.
The examples of isolated microorganisms capable of decomposing a volatile chloroorganic compound are given as follows. As known TCE decomposing strains are, for example, Welchia alkenophila sero 5 (U.S. Pat. No. 4,877,736, ATCC 53570), Welchia alkenophila sero 33 (U.S. Pat. No. 4,877,736, ATCC 53571), Methylocystis sp. strain M (Agric. Biol. Chem., 53, 2903 (1989), Biosci. Biotech. Blochem., 56, 486 (1992), ibid. 56, 736 (1992)), Methylosinus trichosporium OB3b (Am. Chem. Soc. Natl. Meet. Dev. Environ. Microbiol., 29, 365(1989), Appl. Environ. Microbiol., 55, 3155 (1989), Appl. Blochem. Biotechnol., 28, 877 (1991), Japanese Laid-Open Patent Application No. 2-92274, Japanese Laid-Open Patent Application No. 3-292970), Methylomonas sp. MM2 (Appl. Environ. Microbiol., 57, 236 (1991)), Alcaligenes denitrificans ssp. xylosoxidans JE75 (Arch. microbiol., 154, 410 (1990)), Alcaligenes eutrophus JMP134 (Appl. Environ. Microbiol., 56, 1179 (1990)), Mycobacterium vaccae JOB5 (J. Gen. Microbiol., 82, 163 (1974), Appl. Environ. Microbiol., 54, 2960 (1989), ATCC 29678), Pseudomonas putida BH (Journal of Japan Sewage Work Assosiation, 24, 27 (1987)), Acinetobactor sp. strain G4 (Appl. Environ. Microbiol., 52, 383 (1986), ibid. 53, 949(1987), ibid. 54, 951 (1989), ibid. 56, 276(1990), ibid. 57, 193 (1991), U.S. Pat. No. 4,925,802, ATCC 53617, this strain was originally classified as Pseudomonas cepacia then classified into Acinetobactor sp.), Pseudomonas mendocina KR-1 (Bio/Technol., 7, 282 (1989)), Pseudomonas putida F1 (Appl. Environ. Microbiol., 54, 1703 (1988), ibid. 54, 2578 (1988)), Pseudomonas fluorescens PFL12 (Appl. Environ. Microbiol., 54, 2578 (1988)), Pseudomonas putida KWI-9 (Japanese Laid-Open Patent Application No. 6-70753), Pseudomonas cepacia KK01 (Japanese Laid-Open Patent Application No. 6-227769), Pseudomonas sp. (Japanese Laid-Open Patent Application No. 2-273599), Nitrosomonas europaea (Appl. Environ. Microbiol., 56, 1169 (1990)), Lactobacillus vaginalis sp. nov (Int. J. Syst. Bacteriol., 39, 368 (1989), ATCC 49540) and so on.
Among these known strains which are capable of decomposing pollutants, however, no strain meets the above mentioned conditions necessary in practical use for decomposing aromatic compounds and volatile chloroorganic compounds nor has an adequate decomposing activity.
When considering the decomposition treatment of liquid wastes containing TCE, for example, microorganisms applicable to such treatment must be able to grow and maintain their decomposing activity even in such poor surroundings as the waste water.
It is essential that new microorganisms used for such biological clarification treatment have an adequate decomposing activity to volatile chloroorganic compounds and in addition, preferably they have growth conditions different from those of known microbial strains so as to be applicable to a wider field and in more various ways.